Mass profiles were studied mainly for individual FGs, or small samples, making difficult to extrapolate general conclusions.
Possibly the first mass profiles of FGs to be computed were those of NGC 6482 [1]}, RX J1416.4+2315 [2]}, and ESO 3060170 [3]}. The first two systems shows a mass profile well described by an NFW, with a high central concentration that was interpreted as a sign of early formation. On the other hand, the mass profile of ESO 3060170 showed a flattening in the external regions not compatible with numerical simulations and also confirmed in [4]} out to the virial radius. [5]} studied the mass profiles of 4 FG candidates, finding no differences with normal groups/clusters. Also [6]} studied the mass profile of ESO 3060170, within a sample of 16 relaxed groups and clusters: they found a good agreement with a NFW profile, but it must be noticed that their data reached R \( \sim 200\)  kpc, whereas [3]} and [4]} data reached R \( \sim 500\)  kpc and R \( \sim 1000\)  kpc, respectively. The three mass profiles are comparable within R \( \sim 200\)  kpc and differences with the standard NFW profiles rose in the most external regions. This clarify again the complexity of the comparison when individual FGs are studied using data from different sources, within different radius, and treated with different techniques.
Another two mass profiles for the FGs RXC J0216.7-4749 and RXC J2315.7-0222 were studied in [9]}. Only the latter has a good profile, well fitted, out to \(R_{500}\) , by a NFW profile plus a central stellar component.
